Trenching machine

ABSTRACT

A trenching machine having a vertically swinging boom pivotally mounting a weighted trenching stick with lower trenching teeth and operating means for selectively swinging the boom vertically and the trenching stick horizontally relative to the boom to excavate a trench and releasing the boom and trenching stick to drop freely from an elevated position to fragment hard material encountered in the trenching operation. The trenching stick has telescoping members interconnected by energy absorbing means which isolate from the boom the shock forces produced by the impact of the stick with the ground and cushion relative rebound movement of the members following impact. The boom is raised and released to drop by a winch including a cable having a dead end anchored to the machine by a spring which yields to permit braking of the winch drum after each impact without danger of parting or spilling the cable.

[451 July 31, 1973 United States Patent 1 Doty Primary Examiner-ErnestR. Purser An0meyForrest .l. Lilly i 1 TRENCHING MACHINE Inventor: JohnT. Doty, 2238 E. 21st St., Long Beach, Calif. 90810 Aug. 25, 1971 [57]ABSTRACT A trenching machine having a vertically swinging boom pivotallymounting a weighted trenching [22] Filed:

[21] Appl.No.: 174,705

stick with for selectively swinging the boom vertically and the trenclower trenching teeth and operating means 3mm mmk m t stick horizontallyrelative to the boom to excav trench and releasing the boom andtrenching stic drop freely from an elevated posi U .mm

material encountered in the trenc trenching stick has telescopingmembers interconnected by energy absorbing means which isolate from theboom the shock forces produced by the impact of the stick with theground and cushion relative rebound [56] References Cited UNITED STATESPATENTS movement of the members following impact. The boom is raised andreleased to drop by a winch including a a dead end anchored to themachine by a ring which yields to permit braking of the winch thoutdanger of parting or a v r I 1 1 spilling the cable.

9 Claims, 3 Drawing Figures 78 to Hoist winch drum to Drug winch drumPATENTEBJULB 1 I975 to Hoist winch drum to Drug winch drum John T. Dofy,

INVENTOR.

ATTORNEY TRENCHING MACHINE BACKGROUND OF THE INVENTION 1. Field Thisinvention relates generally to earth working machines and moreparticularly to an improved trenching machine.

2. Prior Art A trenching machine is an earth working machine forexcavating trenches in the ground to receive pipe, electric cables, andthe like. A variety of such trenching machines have been devised. Most,if not all, of these existing machines suffer from the disadvantage ofbeing incapable of trenching in or through hard materials, such asvarious types of earth formations, rocks, and the like. As aconsequence, when such hard materials are encountered, it is necessaryto employ auxiliary equipment to break up the material, which is bothtime consuming and costly.

BRIEF SUMMARY OF THE INVENTION The present invention provides animproved trenching machine which is uniquely constructed to excavatetrenches in both relatively soft and relatively hard materials.Accordingly, when a hard material is encountered in a trenchingoperation, the latter may continue uninterrupted without the need toemploy auxiliary equipment to break up the hard material.

To this end, the trenching machine has a boom pivotally mounted at itsinner end on a vehicle, such as a self-propelled crawler and pivotallymounting at its outer end a weighted trenching device commonly referredto as a trenching stick. Projecting longitudinally from the lower end ofthis trenching stick are trenching teeth. Operating means, such as hoistand drag winches including cables extending between winch drums on thevehicle and the upper and lower ends of the trenching stick, areprovided for raising and lowering the boom and trenching stick andswinging the stick on its pivotal connection to the boom to excavate atrench. The winches may also be operated to release the boom andtrenching stick to drop freely from an elevated position for fragmentinghard material.

According to one important feature of the invention, the trenching stickis uniquely constructed to isolate from the boom and other machine partsthe shock forces produced by impact of the stick with the ground, thusto avoid damage to the boom and other parts. To this end, the trenchingstick is constructed in two telescoping sections interconnected byenergy absorbing springs. When the boom and trenching stick are droppedto fragment hard material, the energy absorbing springs yield followingimpact of the trenching stick with the material to absorb the kineticenergy of the descending boom and upper stick section. The energyabsorbing springs also cushion rebound of the trenching stick sectionsto their normal extended relation following impact.

The hoist winch of the trenching machine is equipped with a brake whichthe operator applies to brake the winch drum following impact of thetrenching stick, with the ground. If the brake is applied too soon, thedescending boom and trenching stick may be retarded by the winch cableprior to impact with a sufficient force to part the cable. On the otherhand, if the brake is applied too late, the cable may spill from thewinch drum, in which case the cable must be properly rewound on thedrum.

According to an additional feature of the invention, the hoist cable hasa dead end which is anchored to the machine by a spring which yields toavoid both parting and spilling of the cable.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a trenchingmachine according to the invention;

FIG. 2 is an enlarged side elevation of the trenching stick of themachine; and

FIG. 3 is an enlarged section taken on line 33 in FIG. 2.

DESCRIPTION OF A PREFERRED EMBODIMENT The trenching machine 10 of theinvention illustrated in the drawings has a vehicle 12, such as acrawler, mounting a rotary platform 14 which turns on a normallygenerally vertical axis. Pivotally mounted at its inner end on theplatform 14, to swing vertically on a normally generally horizontal axis16, is a boom 18. A trenching stick 20 is pivotally mounted on the outerend of the boom 18 to swing on a pivot axis 22 parallel to the innerboom axis 16. Operating means 24 are provided for selectively swingingthe boom 18 vertically and swinging the trenching stick 20 horizontallyrelative to the boom to excavate a trench and for releasing the boom andstick to drop freely from an elevated position to fragment hardmaterial. 7

' The trenching stick 20 has a telescoping construction and includesupper and lower telescoping sections 30, 32. The upper section 30 hasupper and lower tubular members 34, 36 with abutting flanges 38 whichare bolted together to join the members into a rigid unit. A reinforcingrib 40 is welded to the front side of the upper tubular member 34.Welded to the rear side of the upper tubular member 34 adjacent itslower end is a tongue 42 which is attached by a pivot 44 to the outerend of the boom 18.

The lower trenching stick section 32 has an upper tubular member 46rigidly joined at its lower end to a relatively massive lower member 48,referred to as a billet. The upper tubular member 46 slides within thelower tubular member 36 of the upper trenching stick 7 section 30.Welded or otherwise rigidly joined to opposite sides of the tubularmembers 36, 46 are brackets 50. Compression springs 52 are mountedbetween and seat at their ends against these brackets to yieldablyresistrelative telescoping movement of the trenching stick sections 30, 32.The spring brackets 50 mount spring retainers 54 which engage within theends of the springs 52 to locate the springs laterally relative to thebrackets.

Springs 52 yieldably urge the trenching stick sections 30, 32 toextended positions. Extending slidably through the spring brackets 50and centrally through the springs 52 are tie bolts 56 having upper andlower shoulders 58. Between the upper spring brackets 50 and tie boltshoulders 58 are compression springs 60 which surround the bolts andseat against the brackets and shoulders. Tie bolts 56 and springs 60limit relative extension movement of the members 30, 32 and cooperatewith the springs 52 to normally retain the members in their partiallyextended positions of FIG. 1. As will be explained presently, thesprings 52, 60 together constitute an energy absorbing means 62 whichserves to isolate from the boom 18 and other machine parts the shockforce produced by impact of the trenching stick 20 with hard material tobe fractured and to cushion relative rebound extension movement of thestick sections 30, 32 following impact.

At the lower end of the trenching stick 20 are longitudinally projectingtrenching teeth 64. These teeth are rigidly joined to a base plate 66which, in turn, is firmly attached to the lower end of the billet 48.

The operating means 24 of the trenching machine includes a hoist winch68 and a drag winch 70 on the vehicle platform 14. The vehicle 12 ispropelled and the winches 68, 70 powered by an engine 72 on the vehicle.Winches 68, 70 include drums 74, 76. Attached at one end to the hoistdrum 74 is a hoist cable 78. This cable extends from the hoist drumupwardly to and around a pulley 80 on an upstanding frame 82 fixed tothe platform 14, then outwardly to and around a pulley 84 on the upperend of the trenching stick 20, then back to and around a second pulley86 on the frame 82, and finally outwardly to and around a second pulley88 on the upper end of the stick. The outer end of the hoist cable 78,referred to as its dead end, is attached to a bolt 90 which extendscentrally through a spring 92 within the upper trenching stick member34. The upper end of this spring seats against a plate 94 which is fixedwithin the upper stick'member and through which the bolt 90 slidablyextends. The lower end of the spring seats against a shoulder 96 on thelower end of the bolt.

Fixed at one end to the drag winch drum 76 is a drag cable 98. This dragcable extends from the drum over a pulley 100 on the inner end of theboom 18, then outwardly to and around a pulley 102 attached by a pivotcdlink 104 to the rear side of the billet 48, then back to and around asecond pulley 106 on the inner end of the boom, and finally back to thelink 104 to which the cable is attached by a cable socket 108.

In normal trenching operation of the trenching machine, the hoist anddrag winches 68, 70 are operated to raise and lower the boom 18 andswing the trenching stick 20 horizontally relative to the boom toexcavate a trench. More specifically, this trenching operation involvesperiodically swinging the lower end of the stick forwardly relative tothe boom, lowering the boom to engage the trenching teeth 64 with theground, drawing the lower end of the stick toward the vehicle 12 to dragthe teeth rearwardly along the ground, and then elevating the boom andrepeating the procedure until the trench has been excavated to thedesired depth. The machine is then advanced to a new section of groundand the entire operation repeated.

When rock or other hard material is encountered which must be firstfragmented or broken up before trenching can continue, the hoist anddrag winches 68, 70 are operated to elevate the boom 18 and trenchingstick 20 with the latter in a generally vertical attitude over the hardmaterial and then release the boom and stick to drop freely into impactwith the material. The kinetic energy of the descending boom and stick,and particularly the billet 48, drives the trenching teeth 64 into thematerial to break up the latter. This procedure is repeated until thehard material is sufficiently fragmented to permit resumption of normaltrenching operation.

As noted earlier, the energy absorbing means 62 serves the twofoldfunction of isolating from the boom 18 the shock forces produced byimpact of the trenching stick 20 with hard material being fragmented andcushioning rebound movement of the trenching stick sections 30, 32following impact. Thus, each time the trenching stick is released todrop into impact with hard material, the stick sections 30, 32 descendin unison until the lower end of the stick impacts the material. Thelower stick section 32 is then suddenly arrested. The upper sticksection 30 and boom 18, on the other hand, continue to descend withresultant relative telescoping movement of the stick sections andcompression of the springs 52. Compression of these springs graduallyabsorbs the kinetic energy of the descending boom and upper sticksection to arrest the same without any severe shock loading of the boomor other machine parts. Immediately after impact, the compressionsprings 52 reexpand to return the stick sections 30, 32 to their normalextended positions in a relatively high speed rebound motion. Springs 60cushion this rebound of the sections to prevent severe shock loading ofthe tie bolts 56 and spring brackets 50.

Included in the hoist and drag winch controls are brakes for the winchdrums 74, 76. During fragmenting operation of the machine, the hoistwinch brake is applied at the end of each downward stroke of thetrenching stick. If this brake is applied too soon, i.e., before impactof the stick with the ground, a tension load is applied to the hoistcable 78 which tends to part the cable. On the other hand, if the brakeis applied too late, i.e., after impact, continued rotation of the hoistdrum 74 because of its momentum will tend to spill cable from the drum,requiring the cable to be properly rewound on the drum.

The hoist cable spring 92 is provided to prevent such parting andspilling of the hoist cable 78. Thus, if the hoist winch brake isapplied too soon, the spring yields to avoid excessive tension in thehoist cable. On the other hand, if the brake is applied too late, thespring, which is normally partially compressed, even during free fall ofthe trenching stick 20 due to the drag of the hoist cable, expands uponimpact to take up any slack in the hoist cable to prevent spilling ofthe cable. If desired, the dead end of the hoist cable may be anchoredto the vehicle platform 14 through the cable spring 92.

I claim:

1. A trenching machine, comprising:

a vehicle; I

a boom pivotally mounted at its inner end on said vehicle to swingvertically on a normally generally vertical pivot axis;

a weighted trenching stick at the outer end of said boom including anelongated upper member pivotally mounted on the outer end of the boom toswing on a transverse pivot axis below the upper end of the stick andparallel to said inner boom axis, a lower toothed trenching membermovable lengthwise of the upper member, and resilient energy absorbingmeans acting between said members to yieldably resist longitudinalmovement of said lower member relative to said upper member;

operating means for selectively swinging said boom vertically andswinging said trenching stick relative to the boom to excavate a trench,and releasing said boom and stick to drop freely from an elevatedposition to fragment hard material encountered in the trenchingoperation, said operating means comprising winch means for raising andlowering said boom and elevating and then releasing said boom to dropfreely, said winch means including a powered winch drum on said vehicle,a cable attached at one end to said drum and extending between said drumand the outer ends of said boom to raise and lower the boom upon windingof the cable on and unreeling of the cable from the drum, and a springin said cable to permit dropping and braking of the boom without partingof the cable or spilling of the cable from the drum.

2. A trenching machine according to claim 1, wherein said cable springis anchored to and carried by said trenching stick.

3. A trenching machine according to claim 1, wherein said cable extendsin a number of runs around pulleys on said vehicle and the outer end ofsaid boom to reduce the load on said cable spring.

4. A trenching machine according to claim 1, wherein said cable isconnected to the upper end of said trenching stick, whereby said winchmeans may be operated to swing the lower end of said trenching stickaway from said vehicle, and

said operating means comprises a second winch means including a secondpowered winch drum on said vehicle and a second cable attached at oneend to said second drum and extending between said lattcr drum and thelower end of said stick, whereby said second winch means may be operatedto swing the lower end of said trenching stick toward said vehicle.

5. A trenching machine according to claim 4, wherein said trenchingstick members comprise telescoping members;

said energy absorbing means comprise springs for resisting relativetelescoping movement of said members to cushion impact of said lowermember with hard material to be fractured and springs for resistingrelative extension movement of said members to cushion relative reboundmovement of the members under the force of said first mentioned springsfollowing impact, and

said lower trenching stick member comprises a relatively massive billetand projecting teeth on the lower end of the billet.

6. A trenching machine according to claim 5, wherein said cable springis contained within the upper end of said trenching stick and isanchored to said upper stick member.

7. A trenching machine, comprising:

a vehicle;

a boom pivotally mounted at its inner end on said vehicle to swingvertically on a normally generally vertical pivot axis;

a weighted trenching stick pivotally mounted on the outer end of saidboom to swing on a transverse pivot axis of the stick parallel to saidinner boom axis and having projecting trenching teeth at the lower endof the stick; and

operating means for selectively raising and lowering said boom andswinging said trenching stick on its pivotal connection to said boom toexcavate a trench, and releasing said boom and stick to drop freely froman elevated position to fracture hard material encountered in thetrenching operation, said operating means comprising a winch means toraise, lower and release said boom to drop freely including a poweredwinch drum on said vehicle, a cable attached at one end to said drum andextending between said drum and the outer end of the boom, and a springanchored at one end to said machine and attached at its other end to theother end of said cable to permit braking of said boom at the end of itsdrop without parting of the cable or spilling of the cable from saiddrum.

8. A trenching machine according to claim 7,

wherein said spring is carried by said trenching stick.

9. A trenching machine according to claim 8, wherein said spring iscontained within the upper end of said trenching stick and is anchoredto the upper stick member.

1. A trenching machine, comprising: a vehicle; a boom pivotally mountedat its inner end on said vehicle to swing vertically on a normallygenerally vertical pivot axis; a weighted trenching stick at the outerend of said boom including an elongated upper member pivotally mountedon the outer end of the boom to swing on a transverse pivot axis belowthe upper end of the stick and parallel to said inner boom axis, a lowertoothed trenching member movable lengthwise of the upper member, andresilient energy absorbing means acting between said members toyieldably resist longitudinal movement of said lower member relative tosaid upper member; operating means for selectively swinging said boomvertically and swinging said trenching stick relative to the boom toexcavate a trench, and releasing said boom and stick to drop freely froman elevated position to fragment hard material encountered in thetrenching operation, said operating means comprising winch means forraising and lowering said boom and elevating and then releasing saidboom to drop freely, said winch means including a powered winch drum onsaid vehicle, a cable attached at one end to said drum and extendingbetween said drum and the outer ends of said boom to raise and lower theboom upon winding of the cable on and unreeling of the cable from thedrum, and a spring in said cable to permit dropping and braking of theboom without parting of the cable or spilling of the cable from thedrum.
 2. A trenching machine according to claim 1, wherein said cablespring is anchored to and carried by said trenching stick.
 3. Atrenching machine according to claim 1, wherein said cable extends in anumber of runs around pulleys on said vehicle and the outer end of saidboom to reduce the load on said cable spring.
 4. A trenching machineaccording to claim 1, wherein said cable is connected to the upper endof said trenching stick, whereby said winch means may be operated toswing the lower end of said trenching stick away from said vehicle, andsaid operating means comprises a second winch means including a secondpowered winch drum on said vehicle and a second cable attached at oneend to said second drum and extending between said latter drum and thelower end of said stick, whereby said second winch means may be operatedto swing the lower end of said trenching stick toward said vehicle.
 5. Atrenching machine according to claim 4, wherein said trenching stickmembers comprise telescoping members; said energy absorbing meanscomprise springs for resisting relative telescoping movement of saidmembers to cushion impact of said lower member with hard material to befractured and springs for resisting relative extension movement of saidmembers to cushion relative rebound movement of the members under theforce of said first mentioned springs following impact, and said lowertrenching stick member comprises a relatively massive billet andprojecting teeth on the lower end of the billet.
 6. A trenching machineaccording to claim 5, wherein said cable spring is contained within theupper end of said trenching stick and is anchored to said upper stickmember.
 7. A trenching machine, comprising: a vehicle; a boom pivotallymounted at its inner end on said vehicle to swing vertically on anormally generally vertical pivot axis; a weighted trenching stickpivotally mounted on the outer end of said boom to swing on a transversepivot axis of the stick parallel to said inner boom axis and havingprojecting trenching teeth at the lower end of the stick; and operatingmeans for selectively raising and lowering said boom and swinging saidtrenching stick on its pivotal connection to said boom to excavate atrench, and releasing said boom and stick to drop freely from anelevated position to fracture hard material encountered in the trenchingoperation, said operating means comprising a winch means to raise, lowerand release said boom to drop freely including a powered winch drum onsaid vehicle, a cable attached at one end to said drum and extendingbetween said drum and the outer end of the boom, and a spring anchoredat one end to said machine and attached at its other end to the otherend of said cable to permit braking of said boom at the end of its dropwithout parting of the cable or spilling of the cable from said drum. 8.A trenching machine according to claim 7, wherein said spring is carriedby said trenching stick.
 9. A trenching machine according to claim 8,wherein said spring is contained within the upper end of said trenchingstick and is anchored to the upper stick member.